Automatic following systems have wide applications in automobiles, sports, entertainment, and even toys. As an illustration, a following systems may be employed in a golf cart application. To play golf, a golfer always needs to bring a club bag around a golf course. While a club bag is necessary, it is often too heavy or cumbersome to be conveniently carried. Currently, a player has several choices. First, the player can pay for a caddie to carry the club bag. A drawback is that paying for a caddie is expensive. Second, the player can drive a golf car. This option is less expensive than hiring a caddie, but the golf car might be restricted from some areas. Third, the player can pull a golf cart or simply carry the club bag. However, pulling the golf cart or carrying the bag can make the game less enjoyable. Fourth, the player might use a battery-powered electronic cart.
Current electronic golf carts offer manual control buttons on the cart. A golfer can then set cart speed, and command it to move or stop. Some carts are even equipped with remote controllers so that a golfer can control a cart from a distance. However, none of the existing carts has automatic following capability. Therefore, these carts have the following drawbacks. First, a golfer still needs to worry about controlling the cart. Second, a golf cart may hit a person and cause injury. Third, a golfer may lose balls because of distractions caused by controlling the golf cart.
Automatic tracking, following, or positioning systems determine the position and moving characteristics of a moving object to be followed. Most of the systems use two methods to accomplish this. One method is a so-called "dead beacon" where multiple reference signals are transmitted at fixed locations and a moving object of interest detects the reference signals to compute its location. Such location information can then be made available to the following object. This is the method used in systems with Loran and GPS. The second method is to permit the moving object to transmit reference signals to the following object. The following object detects the reference signal to find out the position of the object to be followed. To find distance and orientation information, the following object usually has spatially distributed detectors. Signals received by the detectors can be used to compute the distance and orientation by triangulation.
There are several drawbacks to the above-mentioned approaches. The first approach requires the setup of a reference system. As a result, the system is expensive, hard to maintain and the working environment is limited. The GPS and Loran systems offer convenient global position reference, but they do not offer enough accuracy for real-time close following as required in certain applications such as golf carts. The second approach has in itself several drawbacks. First, a reference signal needs to be transmitted continuously from an object to be followed to the following object. This puts a strong restriction on its applications for portable use. Using a golf cart or luggage cart as an example, the object to be followed is a person and the following object is a cart. The person needs to carry a transmitter to send out a strong tracking signal. This transmitter which sends out strong signals has a high power consumption, and therefore would require a prohibitively large battery to energize the transmitter. It is therefore highly impractical to use this method for such applications. Secondly, this method puts a limitation on the use of directional signals (i.e., signals transmitting in small angles, such as infrared signals). This is because the body movement of the carrier may cause detection error. Third, in a multi-cart following case, the following carts may follow the wrong person. Fourth, the method does not offer obstacle detection capability.
Accordingly, it is an object of the present invention to provide an automatic following system which overcomes the above-mentioned drawbacks and disadvantages.